[Lurking Libertarian]

However, for most applications, gravity is well approximated by Newton’s law of universal gravitation,

...for most applications on the surface of the earth, yes. But if NASA had used Newton's equation to plot the course of the Apollo missions to the moon, they would have missed.

[InterceptPoint]

As I recall Newton wasn’t good enough for the GPS System either.

[dr_lew]

...for most applications on the surface of the earth, yes. But if NASA had used Newton's equation to plot the course of the Apollo missions to the moon, they would have missed.

That's a new one on me! Where do you get that? You know, they had "course corrections" in flight, and surely the uncertainties that these accounted for were much greater than the discrepancy between Newton and Einstein.